This Program Project is a multi-disciplinary research effort focused on understanding the genetics, expression, and function of human immune receptor genes and proteins. Major emphasis is on how immunoreceptor genes and lymphoid-specific oncogenes are regulated, mutated, and function. In some instances the studies are on deliberately produced hybridomas, in others, on spontaneous transformations which occur during human malignancies such as acute and chronic lymphatic leukemia, in others, viral transformants are used. Three projects are proposed, bringing together three independent investigators around three core components. One core laboratory provides cell culture facilities for all members of the Program Project. A second core provides molecular biology expertise, while a third core is an administrative unit.